This invention pertains to methods for polishing glass or glass ceramic substrates used to manufacture of magnetic disks. This invention also pertains to slurry compositions for polishing such glass or glass ceramic substrates
A typical prior art process for manufacturing a magnetic disk comprises the following steps:
1. A substrate is polished and textured. PA1 2. An underlayer (e.g. Cr, an alloy of Cr, NiP, NiAl or other materials), a magnetic alloy layer (e.g. a Co alloy), and a protective overcoat (e.g. carbon or hydrogenated carbon) are sputtered, in that order, onto the substrate. PA1 3. A lubricant layer is applied to the protective overcoat. Typical substrates used for magnetic disks comprise NiP-plated aluminum, chemically strengthened glass, or glass-ceramic. PA1 1. Slurry particles have a tendency to "settle". It would be desirable to slow the rate of settling. PA1 2. It would also be desirable to prevent the slurry from foaming during use. PA1 3. It would also be desirable to ensure that the slurry is "redispersible." By redispersible, I mean that if the slurry particles settle, they can be redispersed within the slurry.
It is necessary to polish a glass or glass ceramic substrate before depositing the various layers thereon. The most effective polishing slurries for polishing glass contain CeO.sub.2, ZrO.sub.2, or Fe.sub.2 O.sub.3. Of these, CeO.sub.2 is the most commonly used.
It would be desirable to increase the polishing rate exhibited by slurries. However, in doing so, there are several slurry characteristics one would want to improve.